Count selector



Qct.'14, 1947 G. D. HULST, JR 2,428,913

COUNT SELECTOR Filed Dec. 10, 1945 4' Sheets-Sheet 1 IN VEN TOR.

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Oct. 14,1941 G, D, Hu JR 2,428,913

COUNT SELECTOR File d Dec. 10, 1943 4 Sheets-Sheet s amp/ma 9 LEVEL IN V EN TOR.

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' ATTOB/VEX Patented Oct. 14, 1947 COUNT SELECTOR George D. Hulst, Jr., Millburn, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application December 10, 1943, Serial No. 513,803

14 Claims.

This application concerns a new and improved method and means for selecting from a series of counts such. as produced in a counter type frequency divider of the type shown in E. L. C. White U. S. Patent #2,113,011, dated April 5, 1938, any one particular count. In my method and means a wave is produced on which an incident is caused to occur in time sequence with the selected count. The said selection may be for the purpose of investigation or observation of the count or pulse selected, or for the selection of the time interval at which the selected count occurs and hence for the detailed observation of some event which occurs concurrently with the said selected count. For instance, the pulse wave wherein the event occurs, that is, to be observed, may be applied to a cathode ray tube grid controlling the electron stream intensity to leave Visible on the target only that portion of the trace to be observed and eliminate the remaining portion of the trace.

The selected count which is a fraction of the frequency of the first mentioned series of counts may also be used as a blanking voltage or sweep voltage or a voltage for triggering a circuit, etc., or for producing such a voltage. In addition, the wave wherein the incident occurs may be applied to the electron stream deflecting elements of a cathode ray tube to deflect the pattern on the target thereby permitting observation of the event or incident.

In a sense then my invention may be said to pertain to frequency dividers, since in my improved method and means I select any one of a chain of pulses or counts, and at the output of my improved method and means is provided a new wave wherein a feature thereofrecurs at the rate at which the series or chains of pulses or counts recurs.

An object of my invention is a new and improved circuit for selecting for examination a pulse or count from a chain of pulses or counts which means is flexible in operation.

Another object of my invention is a new and improved circuit for selecting and making available for use in any manner a selected count or pulse occurring in a chain of counts or pulses, which chain of counts or pulses is recurring at a particular rate.

An additional object of my invention is a new and improved circuit for selecting from recurring series or chains of counts or pulses selected counts or pulses and generating from said selected counts or pulses a new wave having a.

clipping action of. tube T2.

2 feature or discontinuity which recurs at the rate of recurrence of the chains of counts.

Additional objects of my invention and the manner in which they are attained will appear from the detailed description of my method and means which follows. In this description reference will be made to the attached drawings wherein Fig. 1 shows graphically a chain of counts or pulses and represents graphically the voltage Egl applied to the grid of tube Tl of Fig. 2.

Fig. 2 is a wiring diagram of one modification of the invention. 7

Fig. 3 shows graphically the voltage Epl on the plate of tube TI resulting from the selection of a particular count or pulse in the chain of counts or pulses Egl. In the example given, the third pulse or count has been selected.

Fig. 4 shows graphically the voltage E'g2 obtained at point I0, in Fig. 2, this voltage being a combination of the efiects of voltage Epl out of the tube TI and the voltage Egl applied thereto. This figure also shows the clipping level of voltage Eg2.

Fig. 5 illustrates graphically the voltage E102 at the output of tube T2 when operated as specified.

Figs. 6 and 7 are graphs illustrating operation of the arrangement of Fig. 2 when the fifth count as represented by Egl is selected.

Figs. 8 to 15 are modifications of the arrangement of Fig. 2. In the modifications of Figs. 12, 13, 14 and 15 the counts are represented by voltages E'gl, which decrease by steps.

In my system a chain of pulses or counts represented by voltages Egl (Fig. 1) which increase progressively in amplitude are impressed from source I on the grid 4 of tube TI of Fig. 2. The cathode of tube TI is connected to a-positive point on an adjustable bias source Ecl, the negative terminal of which is connected through the source I to the control grid 4, so that the bias Ecl 0n the grid 4 with respect to the cathode may be adjusted from a point of substantially equal (ground) potential to a relatively high negative value. The control grid 4 is also coupled v by a condenser 8 and resistance R2 tothe control grid l6 of tube T2. The anode I of tube TI is connected by condenser I2 and a second resistance Rl to the control grid 16. In the preferred form the source of bias E02 biases the grid of T2 to such a point that only the desired pulse will be transmitted to the output connections. The rest of the input wave being removed by the The anode and 3 cathode of tube T2 has means for coupling thereto a utilization circuit.

In operation, it is assumed that the voltage Egl, which increases in a series of steps as shown in Fig. 1, is applied to the grid 4 of tube TI. This voltage may be derived in any manner, for example, it may represent the output of a cycle counter wherein a voltage is built up in steps until a critical point is reached at which time the voltage drops to its original value and the cycle is repeated. The point at which the tube TI is cut off depends upon the voltage E! and the latter depends upon the adjustment of the source represented by Ecl.

At a selected point during the count the tube TI begins to draw current whereupon this tube functions as an amplifier with a gain of somewhat less than the mu of the tube. The amplified voltage appearing across the tube load impedance, represented by BL, is of the form illustrated at Epl in Fig. 3, and depends upon the voltage Egl of Fig. 2. The condensers 8 and [2 are coupling condensers. The resistors RI and R2 form a combining network and are of such magnitude that the signals from the grid and plate linearly mixed therein are mixed in equal proportions. The manner in which these Voltages are mixed is illustrated in Figs. 3 and 4, where Epl represents the voltages at the plate of tube TI and Egl represents the voltage on the grid of tube TI and in the network. The voltages Egl and Epl are so proportioned in mixing that a desired resultant voltage E92 is provided on the grid of tube T2. As a consequence of this mixing of voltages I supply to the grid of tube T2 a voltage Eg2 which may be as illustrated in Fig. 4, where E'gl is the desired portion of Egl and E'pl is the desired portion of Epi.

In the arrangement illustrated it is assumed that the cutofi bias of tube TI is such that it is overcome by Egl at the start of the third from the last count in the chain of counts. The tube Tl then draws current through RL and the voltage on its anode falls ofi in decreasing steps as shown at E'pi in Fig. 4 as the voltage Egl increases past cutoff through the remaining steps of the series of counts. Note that the successive steps by which the plate potential Epl decreases are considerably greater than the steps by which the voltage E'gl increases. The amount of difference depends upon the gain of tube TI and the values of the elements of the mixing network.

As stated above, the voltage E92 may be utilized in any manner such as upon an indicator for counting purposes or supplied to a utilization circuit. When used for indicating purposes note that the sensitivity and accuracy of the indication is enhanced due to the fact that the original counts of each chain the number of counts of which is known is represented by a single count.

In a particular use the voltage is supplied to a tube T2 the grid of which is biased negative to such a value that the maximums of voltage E92 only overcomes the tube cutoif. This tube may be considered a clipping tube and may. be biased to operate at the clipping level as shown in Fig. 4. This tube then has an output as illustrated in Fig. 5 of the drawings.

By selecting a d fferent count in the chain of counts Egl, say for example the fifth count, a voltage Epl of constant amplitude is derived. Then Eal is mixed in the network with a 0.0 1.-

4 stant plate voltage Epi to produce a voltage Eg2 as shown in Fig. 6, similar in appearance to Egl. The voltage Ep2 is then as shown in Fig. 7 when the clipping level is as shown in Fig. 6. The count selection is by adjustment of source Ecl.

Note that the chain of counts or pulses represented at Egl has now been divided to provide a single pulse for 'each group ofv pulses. Moreover, it is noted that by adjustment of Ecl any desired count or pulse of the chain Egl can be caused to overcome the cutoff bias on tube TI and start this tube to amplifying to supply an output Epl which when mixed with Egl provides a voltage at Eg2 which is maximum at an earlier or later point in the cycle of operation so that the pulses at the output of tube T2 as illustrated in Fig. 5 may be moved along the horizontal axis as desired. That is, thesepulses may be made to recur in point of time in synchronism with any one of the counts represented by Egl.

An essential feature of my method and means is means for clipping a voltage of the nature of Egl at a selected point, means which may be included with the first means for inverting the clipped voltage, a means for mixing the inverted voltage with the original step voltage and a further means for clipping the resulting voltage. In Fig. 2 the tube TI serves the first clipping action and the inverting action, the network mixes the voltages and the tube T2 functions as the second clipper. The various components for performing these functions may be arranged in various manners and the sequence of the operations between the first and final clipping action may be altered without altering the principle of operation. The arrangement of Fig. 2 may be considered in general terms as being composed of the above elements arranged as in Fig. 8. In Fig. 8 then there is a first clipper to select the desired count as is done by the biased tube Tl of Fig. 2. This clipper may however, be a biased diode and then its output will not be reversed as in Fig. 1 but will be as shown by the graph between 20 and 22 designated Ep3. The inverter 22 serves the purpose of the tube Tl action by virtue of the reversing efiect in its plate circuit as derived by using the potential drop across RL. The output of this inverter is shown by the graph Epi to the right and below 22. The mixer 24 is a network RI and R2, Fig. 2, or other means for bringing the voltage Egl and Epl together to derive the voltage E92. The voltage clipping means in 26 may be a tube such as tube T2 of Fig. 2 or a biased diode. In Fig. 2 the tube T2 not only clips the voltage but inverts the same, as shown by the voltage graph E122. In Fig. 8 a biased diode or similar clipping means is used which does not have the inverting action and the output is then as shown above and to the right of 25.

The phase inverter in 22 may then be an electron discharge tube operating class A with its input coupled to the diode and its output coupled to one branch of the mixer network, the other branch thereof being excited by the original step voltage Egl.

In the embodiment of Fig. 9, Egl is fed to an adjustable clipper 2'3 and to an inverter 22, and thence to a mixer 24 and from the mixer to the sccond clipper 26. Note that the inverter out put E10 3 is a series of downward steps being Egl inverted and as a result the mixer output EgZ 1. 9 h? form shown. Now the second clipper ag s-e is of such polarity that the bottom step is 'segregatedfrom its fellow steps bythe clipping action. A detailed circuit arrangement of the modification shown in 9 is found in Fig. 10.

In Fig. the clipper for selecting the desired count as represented by Egl is the diode tube 20' having its cathode coupled to source Egl byadjustable bias source E0! and a diode load resistance RLI. The voltage Epl which builds up across BL! is clipped with respect to the voltage Egl by virtue of the diode operation. The diode bias is adjusted, by applying positive potential to the diodecathode, sothat Egl has to build up tothe desired selected count before current flows. In the absence of current flow little or no voltage is developed'across RLI but when current-flows the potential drop across RLI builds up. in steps after the critical voltage Egl is reached so that RLlifeeds to the mixing network RIR2 a voltage as indicated at Epl in Fig. 9. The voltage Ego! is in phase with the voltage Egl.

The voltage Egl is also supplied through bias source E03 to the control grid of an amplifier and inverter tube 22 operating class A so that a voltage Ep i is developed across its anode load resistance RL2 which decreases in steps, being similar to the voltage Egl when properly in" verted. This voltage and E32! are supplied to the mixing network RlRZ and proportioined therein to feed a resulting voltage E92 to the diode clipper 2'6. The clipper tube 2'3 has its anode coupled to the negative end of a bias'source E04, the positive side of which is connected by the load resistance RL3 and resistance 25 to the diode cathode. This inverts the voltage E102 because tube Z'E' does not pass current through the resistance RL3 until EgZ becomes sufficiently negative to drop the cathode potential enough to overcome the positive potential placed on the cathode by the source E05. The clipping level may be shown on E92 in Fig. 9, and the output acrossRL3 may be represented by FM in Fig. 9.

The phase inverter need not be a triode tube operating class A but may be any appropriate means which inverts the voltage as desired. For example, a voltage transformer may be used as in Fig. 11.

In the modification of Fig. 11, the voltageEgl is applied to a biased diode 26' wherein the clipping action takes place. The source Ecl is set so that the tube blocks oif all voltages of less strength than say the third count. The third count overcomes the bias and current fiows in 21! to produce in RLI a potential drop Epl of the character shown under the diode connection to one of the primary windings of a transformer 38 having a second primary winding excited directly by Egl. This is the mixing as well as the phase reversing circuit. The two primary windings are so poled that he drop across RLI, i. e., Epl is combined with E'gi in the desired manner and in the desired proportion in the transformer field to produce in the secondary winding of. the transformer as a voltage E92, as shown above 'the connection between the secondary winding and the diode. 2'5 wherein the clipping action takes place. Diode 26 is. biased by diode load resistance RL3 and bias resistance 32 to clip the voltage EgZ as indicated to supply an output across RL3 of the wave form shown. The condenser C and resistance are sufiiciently high to maintain the instantaneous voltage of the most positive portion of. E 2 at or near the plate to cathode voltage of T2 at which current commencesto flow, that is to say, approximately zero bias. It is to be noted-that the modification of Fig. 11. is similar in principle to the arrangement of Fig. 2. Although the voltage across BL! is not reversed or inverted as in Fig. 2, the voltage Eg2 is similar to'the-same voltage in Fig. 2. The inverting or reversing'action takes place in the windings and/or transformer 30 field. The final output F312 is as shown in Fig. 11.

My count selecting method and means is also useful to select any one of a chain of counts which may be represented by steps of voltage of decreasing value such as shown at E'gl in Fig. 12. Counts as represented by Egl in Fig. 12 may be obtained by a counter circuit in general as described hereinbefore but operated to produce an-output' potential that decreases in steps'with the groups of steps-recurring. The voltage Egl may also be obtained by applying the voltage Egl, say of 1, to an inverter such as a linear amplifier or a transformer properly arranged in a'circuit to provide a voltage that-decreases in steps. No claim ismade herein to means for producing the voltage Eg l.

The principle of operation here is as in the prior modification. The operation is obvious by inspection of :Fig. 12 and Fig. 13wherein is shown the essential features of an embodiment illustrated by rectangles in Fig. 12. The voltage E g! is applied to a clipper 20, Fig. 12, which is ad'- justable, andalso to the mixer 24, which may be a. transformer 24, Fig. 13. The clipper in 20 may include a diode 20' with the anode held negative the desired amount by source E0! in series with load resistance RLI. When the counts step down to the selected count the bias is such that the cathode of the tube becomes sufliciently negative relative to the anode so that current flows in RLI to produce thereacross the clipped output Epl which is fed to one of the windings 2'2 of transformer'2 l. The voltage E'gl isfed to the other winding 3|. The winding 22' is so poled as to invert the voltage Epi, Figs. 12 and 13, to provide in effect in the-transformer Windings and field a voltage Epl, Fig. 12. This voltage is-mixed with Eg'l in the transformer 36 andthe voltages so proportioned as to provide in the secondary windinga voltage Eg2, as shown. This voltage is clippedby diode clipper 26 to provide/across RLZ an output E102 as shown.

The inverter may be in the path of the voltage E'g'l betweenthe source of E'gi and the mixer. Such an embodiment is shown. in Figs. 14 and 15.. The diode clipper 20. Fig. 15, operates as described. abovein connectionwith Fig. 13 to provide across BL! a clipped voltage Epl. The winding 22" is excited by E'gl and is so poled as to reverse. the voltage Egl relative to the voltage Egg] on the other primary winding 33 of transformer 24'. The reversed voltage Egl and Epl are. so proportioned that they add or combine to. provide in the secondary Winding of transformer 24f a voltage EgZwhich is clipped at the levelindicated'and overcomesthe bias on the anode of diode 26' (due to resistance 32 and load resistance. RL2) to produce in load resistance RLZ avoltagerepresented at-Ep2. The resistance 32 and, condenser C must have a product RC sufficiently high that acharge on condenser C caused by current passing through 26 is maintained to a sufficient degree throughout duration of entire cycle that it acts as asource of bias forthe desired clipping action.

I claim:

1. In apparatus for selecting any count from a series or chain of counts represented by voltages which change in value from an initial value by steps to a second Value, return to the said initial value and repeat the cycle, a voltage mixer wherein two vcltageseach of which change in value by steps are linearly mixed in the desired proportions, a voltage clipper in a first path having an input excited b said first named voltage and an output coupled to said mixer stage, a second path having an input excited by said first voltag and an output coupled to said mixer stage, a voltage inverter in one of said paths, and an output circuit for said mixer stage.

2. In apparatus for selecting any count from a series or chain of counts represented by voltages which change in value from an initial value by steps to a second value, return to the said initial value and repeat the cycle, a voltage mixer wherein two voltages each of which change in value by steps are linearly mixed in the desired proportions, a voltage clipper in a first path having an input excited by said first named voltage and output coupled to said mixer stage, a second path having an input excited by said first voltage and an output coupled to said mixer stage, a voltage inverter in said first path, and an output circuit for said mixer stage.

3. In apparatus for selecting any count from a series or chain of counts represented by voltages which change in value from an initial value by steps to a second value, return to the said initial value and repeat the cycle, a mixing stage wherein two voltages each of which change in value by steps are linearly mixed in the desired proportions, a voltage clipper in a first path having an input excited by said first named voltage and an output coupled to said mixer stage, a second path having an input excited by said first voltage and an output coupled to said mixer stage, a voltage inverter in said second path, and an output circuit for said mixer stage.

4. In apparatus for selecting any count from a series or chain of counts represented by voltages which change in value from an initial value by steps to a second value, return to the said initial value and repeat the cycle, a mixing stage wherein two voltages each of which change in value by steps are linearly mixed in the desired proportions, a voltage clipper in a first path having an input excited by said first named voltage and an output coupled to said mixer stage, a second path having an input excited by said first voltage and an output coupled to said mixer stage, a voltage inverter in one of said paths, an output circuit for said mixer stage, and a voltage clipper coupled to the output of said mixer stage.

5. In apparatus for selecting any count from a series or chain of counts represented by voltages which change in value from an initial value by steps to a second value, return to the said initial value and repeat the cycle, a mixing network comprising voltage proportioning resistances wherein two voltages each of which change in value by steps are linearly mixed in the desired proportions, a voltage clipper tube excited by said first voltage and having output electrodes coupled to said mixer stage, a second path having an input excited by said first voltage and an output coupled to said mixer stage, a voltage inverter in one of said couplings, and a second clipper tube coupled to said mixer stage.

6. In apparatus for selecting any count from a series or chain of counts which may be repre- 8 sented by a potential which progresses in steps corresponding to said counts from a first value to a second value, returns to said first value and repeats, a discharge tube voltage clipper and voltage reverser having electrodes excited by said potential and included in circuit with a load impedance, means for adjustably biasing the cutoff bias of said tube to a value whereat it is overcome by a potential corresponding to a selected count of said chain of counts, a path having an input excited by said first potential and having an output, a mixing network coupled to said impedance and to the output of said path, the mixed network serving to mix the potentials developed across said impedance with said first potentials to produce in the network a combined potential having a peak value at a time corresponding to the time at which said potential corresponding to said selected count recurs and a tube potential clipper coupled to said mixer network.

'7. In apparatus for selecting any count from a series or chain of counts which may be represented by a potential which progresses in steps corresponding to said counts from a first value to a second value, returns to said first value and repeats, a discharge tube voltage clipper having electrodes excited by said potential and included in circuit with a load impedance, means for adjustably biasing the cutofi bias of said tube to a value whereat it is overcome by a potential corresponding to a selected count of said chain of counts, a path having an input excited by said first potential and having an output, a potential reverser tube having an input coupled to said path output, said last tube having an output, a combining network coupled to said impedance and to the output of said potential reverser, the mixer network serving to mix the potentials developed across said impedance with said first potentials to produce in the network a combined potential having a maximum value at a time corresponding to the time at which said potential corresponding to said selected count recurs and a tube potential clipper coupled to said mixer network.

8. In apparatus for selecting any count from a series or chain of counts which may be represented by a potential which progresses in steps corresponding'to said counts from a first value to a second value, returns to said first Value and repeats, a discharge tube voltage clipper having electrodes excited by said potential and included in circuit with a load impedance, means for adjustably biasing the cutoff bias of said tube to a value whereat it is overcome by a potential corresponding to a selected count of said. chain of counts, a transformer having a, secondary winding and having a first primary winding excited by said first potential and a second winding coupled to said impedance, the polarity of the said windings being such that there is a relative potential polarity reversal in the transformer to mix the potentials developed across said impedance with said first potentials to produce in the secondary winding a resultant potential having a maximum value at a time corresponding to the time at which said potential corresponding to said selected count recurs and a tube potential clipper coupled to said secondary winding.

9, In a system of the class described, a source of voltages which increases in steps from a minimum value to a maximum value and then repeats, a clipper tube excited by said voltages and in a circuit including a load impedance and a bias circuit for adjusting the cutofi bias of said device, a voltage combining circuit coupled with the said impedance and with said source, a voltage reverser in one of said couplings, a second clipper tube having electrodes coupled to said combining circuit for deriving a wave an incident on which recurs in time sequence with recurrence of the selected voltage at which the bias of said first device is overcome.

10. In a system of the class described, a source of voltages which increases in steps from a maximum value to a minimum value and then repeats, a clipper tube excited by said voltage and having electrodes in circuit with an output impedance and with an adjustable source of bias for adjusting the cutoff bias of said tube, a voltage combining circuit coupled with said impedance and with said source, a voltage inverter in one of said couplings, a voltage clipper tube coupled to said combining circuit and biased'to derive a wave an incident on which recurs in time sequence with recurrence of the selected voltage at which the bias of said first device is overcome.

11. In apparatus of the class described an electron discharge device having a control electrode, a cathode and an output electrode, an adjustable bias connecting said cathode to said control electrode for applying to said control grid an adjustable cutoflf bias, connections for applying to said control electrode potential which increases in recurring steps, from a minimum value to a maximum value, a potential combining network, a coupling between said potential combining network and the output electrode of said device and connections for applying said potential which increases in recurring steps to said network whereby a resultant voltage which is a, summation of the voltage applied to the control electrode of said tube and the voltage amplified in said tube is obtained in said network.

12. In apparatus for selecting any count from a series or chain of counts, means for producing a potential which progresses in steps corresponding to said counts from a minimum value to a maximum value, a discharge tube having input and output electrodes, means for adjustably varying the cutoff bias of said tube to a value whereat it is overcome by a potential corresponding to a selected count of said chain of counts, connections for applying said potential to said input electrodes, a combining network and connections for impressing amplified potentials from the output electrodes of said tube and potentials from said first connections on said network to produce therein a combined potential having a maximum value at a time corresponding to the time at which said potential correspondin to said selected count recurs.

13. In apparatus of the class described an electron discharge device having a control electrode, a cathode and an anode, an adjustable bias connecting said cathode to said control electrode for applying thereto an adjustable cutoff bias, connections for applying to said control electrode potential which increases in recurring steps, from a minimum value to a maximum value, a potential combining network, a coupling between said potential combining network and the anode and cathode of said device and connections for applying said potential which increases in steps to said network whereby a resultant potential which is a summation of the voltage applied to the control electrode of said device and the voltage amplified in said device is obtained.

14. In apparatus for selecting any count from a series or chain of counts, means for producing a potential which progresses in steps corresponding to said counts from a minimum value to a maximum value, a discharge tube having input and output electrodes, means for adjustably varying the cutoff bias of said tube to a value whereat it is overcome by a potential corresponding to a selected count of said chain of counts, connections for applying said potential to said input electrodes, a combining network and connections for impressing potential from the output electrodes of said tube and from said first connections on said network, and a second tube having input electrodes coupled to said network and output electrodes coupled to an output circuit.

GEORGE D. HULST, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,266,401 Reeves Dec. 16, 1941 1,927,676 Bedford Sept. 19, 1933 2,217,957 Lewis Oct. 15, 1940 2,266,154 Blumlein Dec. 16, 1941 2,113,011 White Sept. 19, 1933 

